The present invention relates generally to data communication. More particularly, the present invention relates to multiplexing pins of a PC Card for providing audio communication between the PC Card and a host computer.
PC or PCMCIA Cards have been developed to provide additional data processing capabilities in data processing systems such as a personal computer. A PC Card may be plugged into a standard connector and operated in conjunction with the host computer.
The PC Card connector and data interchange formats are standardized. Mechanical and electrical standards have been established to ensure proper connection of PC Card to host. In particular, the PC Card has a 68 pin connector and its pins are in a standardized arrangement. Each pin has a defined function. Standardization ensures that PC Cards from different manufacturers will work in all host equipment.
One limitation to the standardized pin arrangement is in the area of audio processing. The conventional 68 pin PC Card connector includes a single pin for communication of audio from PC Card to host. No provision is made for transmission of audio from the host to the PC Card. Moreover, the one pin available yields poor quality when used for audio. No spare pins are available for further communication of audio.
Audio data could be transferred using the standard PC Card data bus. However, such a design would create a continuous stream of data on the data bus which would put an undesirably large load on the processor of the host.
One prior design has identified a modification to the host computer to permit two way audio communication. In U.S. Pat. No. 5,752,082, the host computer is modified so that digitized audio may be serially transferred between the host and a PC Card with no processor bandwidth. A multiplexer is inserted in the connection between the PC Card socket controller in the host computer and the PC Card socket in the host. The multiplexer either allows regular PC Card signals to pass between the socket controller and the socket or the multiplexer switches digitized audio signals onto the socket.
The earlier design does not address the PC Card side of the interface. Accordingly, an improved PC Card is desirable for providing two way audio when used in conjunction with a host computer.
By way of introduction only, a PC Card in accordance with the present embodiment includes designation of four normally unidirectional signal lines in the PC Connector for bi-directional communication.
The PC Card includes signal drivers having a control input. When the associated pins are inactive, the signal drivers are electrically disconnected from the PC Card pins or placed in a high impedance state. In the inactive mode, the PC Card operates as a conventional PC Card.
When placed in an active mode by asserting the control signal, the signal drivers are electrically coupled to the pins of the PC Card connector for two way communication of digitized audio data.
In one embodiment, the control signal is generated by circuitry in the PC Card. In another embodiment, the control signal is generated by the host and communicated over the connector.